The technology of changing a state of material, such as an ablation or denaturation of physical properties, by irradiating the material with a laser pulse having a short pulse width is attracting attentions in recent years (for example, refer to Japanese Patent No. 3283265 and “Femuto Byo Tekunoroji—Kiso to Oyo— (Femtosecond Technology—Foundation and Application—)”, Kagaku-Dojin Publishing Company, Inc., Kazuyuki Hirao et al., Mar. 30, 2006 (1st edition, 1st issue), pp. 1-13, and pp. 125-134) (hereinafter referred to as the “Non-patent Literature”). Conventionally, as disclosed in the Non-patent Literature and Japanese Patent No. 3283265, a laser ablation of a metal material using the above-mentioned short pulse width is carried out on metal, such as gold and copper, whose melting point is comparatively low. Contrarily, when the laser ablation is carried out to metal, such as molybdenum (Mo) or tungsten (W), which have comparatively high melting points, the obtained effects have not been verified.
Further, technology, such as that disclosed, for example, in Japanese Patent No. 3570414, regarding preventing a discharge medium from leaking out of a high pressure discharge lamp's arc tube when a discharge medium is being enclosed in the arc tube has been developed. Specifically, Japanese Patent No. 3570414 approaches leak prevention by making its sealing portions, which are made of glass and sealing metal pieces, of its high pressure discharge lamp into a special shape with the goal of improving the adhesion strength between the glass and the sealing metal pieces to more airtightly seals the arc tube's sealing portions.
Although the above references do disclose technologies, the separation problem of the glass and the sealing metal pieces is not fully solved. The present invention solves this problem and improves the adhesion strength between the glass and the sealing metal pieces in a sealing portion of a high pressure discharge lamp.